21345131 has 4 divisors (see below), whose sum is σ = 22081200. Its totient is φ = 20609064.

The previous prime is 21345119. The next prime is 21345187. The reversal of 21345131 is 13154312.

It is a semiprime because it is the product of two primes.

It is a cyclic number.

It is not a de Polignac number, because 21345131 - 2⁶ = 21345067 is a prime.

It is a super-2 number, since 2×21345131² = 911229234814322, which contains 22 as substring.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21345101) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 367991 + ... + 368048.

It is an arithmetic number, because the mean of its divisors is an integer number (5520300).

Almost surely, 2^21345131 is an apocalyptic number.

21345131 is a deficient number, since it is larger than the sum of its proper divisors (736069).

21345131 is an equidigital number, since it uses as much as digits as its factorization.

21345131 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 736068.

The product of its digits is 360, while the sum is 20.

The square root of 21345131 is about 4620.0791118768. The cubic root of 21345131 is about 277.3956256013.

Adding to 21345131 its reverse (13154312), we get a palindrome (34499443).

The spelling of 21345131 in words is "twenty-one million, three hundred forty-five thousand, one hundred thirty-one".